The present invention relates to an automatic transmission system for vehicles, and more particularly to a vehicle automatic transmission system of the speed-change-gear type having actuators responsive to electric signals provided in association with the transmission and clutch for automatically carrying out start and gear change operations with reference to predetermined gear-change map data in accordance with parameters indicative of the operating condition of the vehicle, such as the amount of depression of the accelerator pedal.
In such a type of automatic transmission system, insofar as the derived conditions for gear change are satisfied, the gear change operation will be carried out in accordance with predetermined gear change map data independently of the will of the driver. However, under certain conditions it may sometimes be desirable to carry out the gear change operation not on the basis of the gear change map data but on the basis of the will of the driver.
To make this possible, there has, for example, been proposed an automatic transmission system provided with a manual switch for commanding gear change and a manual pattern showing the allowable range for manual operation of gear change. When the switch is operated in the case where the manual operation is in the allowable range, the operation of changing to a higher or lower gear is carried out in response to the operation of the switch, and after this, the gear change operation is automatically returned to the gearshift control based on the automatic gear change pattern (Japanese Patent Application Disclosure Sho No. 58-124853).
However, the proposed system needs a number of switches, such as a shift-up switch, a shift-down switch, a hold switch and the like, so that it has the disadvantages of making driving complicated and is not compatible with the desire to reduce fuel consumption while enhancing operational ease.